The prostate is a male reproductive system gland that is generally made of three lobes that are enclosed by an outer layer of tissue referred to as the capsule. The prostate surrounds the lower portion of the bladder (where urine is stored) and part of the urethra (the canal through which urine passes from the bladder out of the body).
Continued growth of the prostate causes Benign Prostatic Hypertrophy (BPH), where the continually growing prostate tissue squeezes the lower portion of the bladder and the urethra, making it difficult to pass urine.
BPH is often treated by surgically removing the excess prostatic tissue from the interior region of the prostate that is pressing on the urethra, which usually relieves the obstruction and the incomplete emptying of the bladder caused by the BPH, leaving the rest of the prostatic tissue and the capsule intact.
Surgeons often perform transurethral surgery to remove the excess prostate tissue (targeted prostatic tissue). This surgery is performed by inserting a resectoscope through the urethra. The resectoscope is used to view the interior of the urinary tract, and to cut (incise) off pieces of the targeted prostatic tissue. Following surgery, a urinary catheter is inserted into the urethra to drain urine from the bladder. This catheter is usually left in place until the presence of blood in the urine has diminished, usually within 1-4 days.
There are several prostate resection procedures currently being used. The TURP procedure (transurethral resection of the prostate) is a very common treatment of BPH. During a TURP procedure, the surgeon uses a standard electrosurgical cutting loop to remove the obstructing tissue from the prostate. The electrosurgical cutting loop is inserted through the resectoscope to the targeted prostatic tissue. The electrosurgical cutting loop uses electricity to "shave" off small pieces of the targeted prostate tissue from the interior of the prostate. During surgery, the shaved pieces of prostatic tissue are carried by irrigation fluid flowing through the resectoscope into the bladder. At the end of the operation, these pieces of excised prostatic tissue are flushed out of the bladder using irrigant, aspirated out using a large bore syringe, and/or removed through the resectoscope using a grasping device.
The pieces of prostatic tissue excised by the electrosurgical loop must be small enough to flush out with the irrigant, aspirate out using the large bore syringe, or grasped and removed through the resectoscope. Therefore, the surgeon must make many surgical incisions into the targeted prostatic tissue with the electrosurgical cutting loop, each of which resulting in the extraction of a piece of prostatic tissue having limited size and significant bleeding. The more surgical incisions made by the surgeon with the electrosurgical loop, the more opportunity for error. In addition, because there is a high number of excised pieces of prostatic tissue to be removed from the bladder, the flushing, aspiration, and/or grasping methods of tissue removal can be time consuming.
There are also thermotherapy techniques that cook the prostatic tissue to reduce the size of the enlarged prostatic tissue. For example, VLAP (visual laser ablation of the prostate) employs an Nd:Yag laser to irradiate and heat each of the prostatic lobes from within the urethra at a given power for a given time duration. Interstitial thermotherapy uses an Nd:Yag laser and/or microwave energy and injects heat into the lateral lobes of the prostate. Within two months of treatment the affected tissue dies and the cells sluff off and eventually flush out of the patient through their urine. If the laser is used, the laser energy coagulates the treated tissue which limits bleeding and preserves a clearer field of view for the surgeon. Tissue removal using thermotherapy techniques is inefficient, as it takes several months to fully clear the dead tissue from the patient's system. The patient can be catheterized for up to two weeks because of excessive swelling of the prostatic tissue. Also, these procedures are not very precise. It is difficult to control the thermal end point of the affected tissue, and hence difficult to control the extent of ultimate tissue necrosis. There is also no visual indication as to what tissue has been sufficiently heated, and to what depth. Lastly, the dead tissue being flushed out over a long period of time invites infection and causes prolonged irritative symptoms for the patient.
New procedures have been developed with the commercialization of laser systems that exhibit low penetration depths in tissue. For example, erbium (wavelength=2.94 or 2.71 um) and holmium (wavelength=2.1 um) laser systems produce optical outputs that penetrate only a few hundred microns in an aqueous environment. Therefore, side and end firing optical fibers can be inserted through the resectoscope to incise and ablate the prostatic tissue. The laser energy vaporizes the water content of cells and coagulates the underlying tissue, thus significantly reducing the bleeding and swelling that otherwise results from TURP and VLAP, as well as reducing the amount of catheterization time during recovery, while providing immediate relief of the BPH symptoms.
The tissue ablation rate of such laser systems is far too slow to simply use a side or end firing fiber to ablate away all the targeted prostatic tissue. However, holmium and erbium lasers have been used to incise a urination channel in the urethra after a thermotherapy procedure. The urination channel allows for an earlier removal of the catheter.
The HOLRP procedure (holmium laser resection of the prostate), has recently been developed, and uses laser light from a holmium laser system to remove the targeted prostatic tissue. The laser light is transmitted through an optical fiber inserted through the resectoscope to the targeted prostatic tissue. The laser light cuts the excess tissue from the interior of the prostate in much the same way as the electrosurgical loop in TURP, while coagulating the underlying tissue. The excised pieces of prostatic tissue are carried by irrigation fluid flowing through the resectoscope into the bladder. At the end of the operation, these pieces of excised prostatic tissue are flushed, aspirated, or grasped and removed from the bladder (and/or from the urethra (fossa)) in the same manner as the TURP procedure. As discussed above, these pieces of excised prostatic tissue must be of limited size, for removal by irrigation, large bore syringes and/or grasping tools, which can be a time consuming procedure. Further, the surgeon makes as many as 50 to 60 incisions per procedure in order to limit the size of the excised pieces of prostatic tissue, thus increasing the risk of inadvertent damage to surrounding tissue.
All of the above procedures suffer from the limitation that the excised pieces of prostatic tissue must be small enough for removal from the bladder. This limitation requires additional surgeon skill and time in incising the targeted prostatic tissue into small pieces, and more additional time removing all the excised pieces of tissue from the bladder. Prolonging the prostate resection procedure is costly in that it ties up operating room time, and requires the patient to be anesthetized longer thus increasing the risks of this surgical procedure. There is a need for a transurethral prostatic tissue removal method and device that accurately, efficiently and safely incises and removes targeted prostatic tissue from the patient. Ideally, such a method and device would minimize the number of incisions performed by the surgeon, and reduce the time necessary to extract all the excised pieces of tissue from the patient, thus reducing the time the operating room is occupied and the patient is anesthetized.